The present invention relates to an actuator provided in an automatic speed changer of an automotive vehicle for operating a speed change controlling valve for controlling a speed change mechanism.

Conventionally, in an automatic speed changer for an automotive vehicle, particularly, a CVT controller, a rotational ratio between a shaft on an engine side and a drive shaft is adjusted by changing a ratio of diameters between a driven pulley and a drive pulley which are connected to each other by a metal belt. Also, the diameters of the driven pulley and the drive pulley are continuously changed by changing a width of a belt groove of each pulley. Furthermore, the width of the belt groove is changed by moving a drum provided in each pulley. Each drum is moved by a hydraulic circuit, and the speed change controlling valve for controlling the amount of movement thereof is operated by an actuator.

Conventionally, a miniaturized actuator which can operate the above-described speed change controlling valve with high precision under the condition that it may be dipped in a transmission case or oil is splashed is required.

The present invention is made to solve the problems mentioned above, and an object of the present invention is to provide an actuator for operating a speed change controlling valve of an automatic speed changer which can improve an operational precision and reduce the total size and the weight.

To this end, according to one aspect of the present invention, there is provided an actuator for operating a speed change controlling valve of an automatic speed changer, adapted to be disposed within a transmission case for receiving a speed change mechanism and the speed change controlling valve for controlling the speed change mechanism, comprising: a stepping motor having an outer casing member made of resin, a motor body provided within the outer casing member and a shaft rotated by the motor body; a housing made of resin and coupled with the outer casing member; a pipe having a proximal end portion disposed within the housing and a distal end portion projecting from the housing, the pipe being reciprocatingly moved in an axial direction of the shaft for operating the speed changing controlling valve; and a conversion mechanism disposed within the housing for translating a rotation of the shaft into a linear motion of the pipe.

In the accompanying drawings:

• Fig. 1 is a plan view showing an actuator for operating a speed change controlling valve of an automatic speed changer in accordance with a first embodiment of the present invention;
• Fig. 2 is a cross-sectional view taken along a line II-II in Fig. 1;
• Fig. 3 is a cross-sectional view taken along a line III-III in Fig. 2;
• Fig. 4 is a cross-sectional view taken along a line IV-IV in Fig. 2;
• Fig. 5 is an exploded perspective view showing an essential part in Fig. 2;
• Fig. 6 is a sectional view showing an essential part of an actuator in accordance with a second embodiment of the present invention;
• Fig. 7 is a cross-sectional view showing an essential part of an actuator in accordance with a third embodiment of the present invention; and
• Fig.8 is a cross-sectional view showing an essential part of an actuator in accordance with a fourth embodiment of the present invention.

Embodiments of the present invention will now be described below with reference to the accompanying drawings.

Fig. 1 is a plan view showing an actuator for operating a speed change controlling valve of an automatic speed changer in accordance with a first embodiment of the present invention, Fig. 2 is a cross-sectional view taken along a line II-II in Fig. 1, Fig. 3 is a cross-sectional view taken along a line III-III in Fig. 2, and Fig. 4 is a cross-sectional view taken along a line IV-IV in Fig. 2. In the drawings, a PM type stepping motor 1 has an outer casing member 2 made of resin, a motor body 3 provided within the outer casing member 2 and a shaft 4 to be rotated by the motor body 3.

The motor body 3 has a stator 5 fixed to the outer casing member 2 and a rotor 6 fixed to the shaft 4. The stator 5 is provided with a coil 7, a coil terminal 8 drawn from the coil 7 and a connector terminal 9 to which the coil terminal 8 is connected. The connector terminal 9 is connected to an external connector 25. The rotor 6 is provided wit a bush 10 and a permanent magnet 11.

A sleeve-like housing 12 made of resin is coupled with the outer casing member 2. Also, a housing 12 is fastened to the outer casing member 2 by a plurality of screws 12A extending in parallel with the shaft 4. A circular engagement hole 2a is formed in the outer casing member 2 and an engagement portion 12a inserted into the engagement hole 2a is formed on the housing 12. As shown in Fig. 3, three positioning projections 12b which projected radially and are in contact with an inner circumferential surface of the engagement hole 2a are formed on an outer circumferential surface of the engagement portion 12a. Also, an annular groove 12c is formed in the joint surface with the outer casing member 2 of the housing 12.

A housing communication hole 12d for communicating between the inside and the outside of the housing 12 is provided in the side wall of the housing 12. A filter 13 is provided in the housing communication hole 12d for trapping contamination contained in the oil. The shaft 4 is rotatably held by bearings 14 and 15. The bearing 15 fixed within the housing 12 is of a rubber seal type.

A pipe 16 that is reciprocating in the axial direction of the shaft 4 by the rotation of the shaft 4 is provided at a tip end portion of the housing 12. A proximal end portion of the pipe 16 is inserted into the housing 12, and a distal end portion of the pipe 16 is caused to project from the tip end portion of the housing 12. A pipe communication hole 16a for communicating between the interior of the housing 12 and the interior of the pipe 16 is provided in the pipe 16. A sleeve 17 for guiding the linear movement of the pipe 16, an oil seal 18 for preventing the contamination of the pipe 16 from the outer circumferential portion and a ring-shaped stopper 19 for limiting the front and rear movement of the pipe 16 are fixed to the inner circumferential surface of the tip end portion of the housing 12.

Also, as shown in Fig. 5, a screw portion 4a is provided on the shaft 4. A guide member 20 made of resin and engaged with the screw portion 4a is fixed to the proximal end portion of the pipe 16. As shown in Fig. 4, rotation limit projections 20a for limiting the rotation of the pipe 16 are formed to project radially outwardly from the outer circumferential portion of the guide member 20. Accordingly, the guide member 20 is moved in the axial direction of the shaft 4 by the rotation of the shaft 4. A stopper 21 made of metal for limiting the rearward movement of the pipe 16 is fixed to the shaft 4. The guide member 20 and the stopper 21 have stopper surfaces 20b and 21a which are perpendicular to the rotational direction of the shaft 4, respectively.

A conversion mechanism 31 has the screw portion 4a, the guide member 20 and the stopper 21. An operating member 22 made of resin and engaged with a rotatable lever 30 connected to a speed change controlling valve (not shown) is mounted at the tip end portion of the pipe 16.

The operation will now be described. When a current is caused to flow through the outer connector 25, the coil 7 is excited so that the rotor 6 and the shaft 4 are rotated together. Since the guide member 20 is engaged with the screw portion 4a of the shaft 4 and the rotation of the guide member 20 is limited, the rotation of the shaft 4 is translated into the linear motion of the guide member 20 and the pipe 16. Since the operating member 22 is mounted at the tip end portion of the pipe 16 and the operating member 22 is engaged with a U-shaped groove of the lever 30, when the pipe 16 is moved, the lever 30 is swung to thereby operate the speed change controlling valve.

In such an actuator, since the lever 30 is operated by using the stepping motor 1 and the conversion mechanism 31 received in the housing 12, it is possible to improve the operational precision in the oil, and to reduce the total size and the weight. Also, since the housing 12 is positioned by forming the positioning projections 12b at the engagement portion 12a, if only the precision of the positioning projections 12b is determined with a high precision, even if the outer casing member 2 and the housing 12 are made of resin, it is possible to prevent the displacement of the housing 12 or the tilt of the housing 12 and the pipe 16 to the shaft 4. It is thus possible to perform assembling with a high precision and to reduce the total size and the weight.

Furthermore, since the housing communication hole 12d for communication between the inside and the outside of the housing 12 is formed in the housing 12, even if it is dipped into the oil in the transmission case, the pressure difference generated between the inside and the outside of the housing 12 is suppressed, and the pipe 16 can be moved smoothly. Also, since the filter 13 is provided in the housing communication hole 12d, it is possible to prevent the contamination in the oil from entering the housing 12 and to maintain the smooth motion of the pipe 16.

Furthermore, since the annular groove 12c is formed in the joint surface between the outer casing member 2 and the housing 12, in the case where the oil enters through a slight gap around the joint surface, the contamination can be entrapped by the groove 12c to thereby maintain the normal operation of the stepping motor 1. Also, since the rubber seal type bearing 15 is provided at tee end portion, on the stepping motor 1 side, of the housing 12, it is possible to prevent the contamination from invading from the housing 12 into the motor body 3.

Furthermore, the operating member 22 is made of resin that is superior in anti-wear property and slidability so that the lever 30 can be stably operated for a long period of time. Moreover, since the pipe communication hole 16a for communicating between the interior of the housing 12 and the interior of the pipe 16 is provided in the pipe 16, it is possible to smoothly move the pipe 16 in a linear manner. Also, since the stopper surfaces 20b and 21a perpendicular to the rotational direction of the shaft 4 are formed on the guide member 20 and the stopper 21, respectively, to thereby limit the rearward movement of the pipe 16, it is possible to maintain the position of the rear end of the pipe 16 more accurately.

Furthermore, since the advance movement of the pipe 16 is limited by the stopper 19 fixed within the housing 12, the structure can be simplified. Furthermore, since the resin-made sleeve 17 is fixed within the housing 12 to guide the linear motion of the pipe 16, it is possible to stabilize the linear motion of the pipe 16 with a simple structure.

Incidentally, in the foregoing embodiment, the positioning projections 12b are formed on the outer circumferential surface of the engagement portion 12a of the housing 12, but, for example, as shown in Fig. 6, a flat positioning projection 2b may be formed in the inner circumferential surface of the engagement hole 2a of the outer casing member 2. Also, the positioning projection may be formed on both the housing 12 and the outer casing member 2.

Also, in the foregoing embodiment, the annular groove 12c is formed in the joint surface of the housing 12 with the outer casing member 2, but, for example, as shown in Fig. 7, 12c and 2c may be formed on both the housing 12 and the outer casing member 2 and the groove may be formed only in the outer casing member 2.

Furthermore, in the foregoing embodiment, the advance movement of the pipe 16 is limited by the stopper 19, but, for example, as shown in Fig. 8, the guide member 20 may be brought into contact with the sleeve 17 for guiding the linear motion of the pipe 16 to thereby limit the advance movement of the pipe 16.

Various details of the invention may be changed without departing from its spirit nor its scope. Furthermore, the foregoing description of the embodiments according to the present invention is provided for the purpose of illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.